1. Field of the invention
The present invention generally relates to a refractometer of an eye and, more particularly, to an apparatus for measuring the refractive power of an eye.
2. Description of the Related Art
Various refractometers for measuring the refractive power of an eye are known. The refractometer observes a spot pattern formed on the eyeground, namely, the retina of the eye to be examined (hereinafter referred to as eye) through an optical system so as to measure the refractive power of the eye. Before the refractive power of an eye is measured, it is necessary to adjust the position of the measuring optical system of the refractometer with respect to the eye to a measurable state, namely, the state in which the axis of the eye aligns with that of the measuring optical system and the optical pattern is formed on the retina of the eye in an in-focus condition. According to known refractometers, it is necessary for a patient to fix his eye on the visual target for several to several tens of seconds before the refractometer is capable of measuring the refractive power of eye. To this end, the patient has his forehead, chin or cheek fixed to a head fixing member. The known refractometer comprises, as shown in FIG. 28, a head fixing member 62 mounted on one end portion of a base 61, a main body 63 which is moved on the base 61 by a moving mechanism included therein, an optical measuring device 64 mounted on the main body 63, and a joy stick 65. In this construction, the joy stick 65 is operated to move the main body 63 in the lengthwise, widthwise, and vertical directions thereof so that the optical measuring device 64 is adjusted to precisely confront the eye fixed to the head fixing member 62. Thus, the known refractometer or automatic refractometer forces the patient to take an uncomfortable posture for a predetermined period of time. Thus, the patient is required to have concentration while his eye is being measured. In addition, even an adult must have patience during this period of time. Such being the case, it is very difficult to examine infants' eyes.
In the known refractometer, the refractive power of eye is measured under a condition where when the an optical pattern is correctly formed on the retina. Optical elements such as a slit and a lens are required to be movably mounted on the light projecting optical system which projects a light of the optical pattern or on the light receiving optical system which receives the light of the optical pattern reflected from the retina. This construction prevents a compact light measuring optical system and a device containing the light measuring optical system from being manufactured. Since the apparatus for measuring the refractive power of an eye has the construction as described above, the apparatus is fixed to a table. When the refractive power of an eye of a patient who is so serious that he cannot rise on the bed is measured, a particular device is required to be prepared. As such, the known apparatus has various disadvantages to be overcome.